split string only on first instance of specified character

In my code I split a string based on _ and grab the second item in the array.

var element = $(this).attr('class');
var field = element.split('_')[1];

Takes good_luck and provides me with luck. Works great!

But, now I have a class that looks like good_luck_buddy. How do I get my javascript to ignore the second _ and give me luck_buddy?

I found this var field = element.split(new char [] {'_'}, 2); in a c# stackoverflow answer but it doesn't work. I tried it over at jsFiddle...